1. Field of the Invention
The present invention generally relates to flat-panel display devices, and more particularly to a plasma display device.
A plasma display device is a flat-panel display device of a light-emitting type that displays picture information by selectively inducing discharges in a gas filled between a pair of glass substrates.
It is important for the plasma display device to increase resolution and reduce power consumption at the same time.
2. Description of the Related Art
FIG. 1 is a diagram showing a basic structure of a conventional common plasma display device 10.
The plasma display device 10 is basically defined by a display panel 11 and first through third driving circuits 12A through 12C that cooperate with the display panel 11. The display panel 11 includes first discharge electrodes X1 through Xm and second discharge electrodes Y1 through Ym that are alternately arranged parallel to each other and extend in the X direction of FIG. 1. Further, the display panel 11 includes address electrodes A1 through An that extend in the Y direction of FIG. 1 to intersect the first and second discharge electrodes X1 through Xm and Y1 through Ym. The first discharge electrodes X1 through Xm, the second discharge electrodes Y1 through Ym, and the address electrodes A1 through An are selectively activated by the first through third driving circuits 12A through 12C, respectively.
For instance, an address voltage is applied between a selected one of the first discharge electrodes X1 through Xm (X2 in FIG. 1) and a selected one of the address electrodes A1 through An (A4 in FIG. 1), so that a discharge is started between the first discharge electrodes X2 and the address electrode A4. Next, by applying a discharge-sustaining voltage between the first discharge electrodes X2 and the adjacent second discharge electrode Y2 by the driving circuits 12A and 12B, a discharge is started between the first discharge electrodes X2 and the second discharge electrode Y2 in a display cell selected by the address electrode A4. The discharge is maintained while the selected display cell is activated.
It is required for such a plasma display device to increase resolution by narrowing pitches between electrodes and reduce power consumption at the same time.
FIG. 2 is a sectional view of the conventional plasma display panel 11, whose type is referred to as an ALIS (Alternate Lighting of Surfaces) type, taken along the Y direction of FIG. 1. This type of plasma display panel is disclosed in Japanese Patent No. 2801893.
The display panel 11 of FIG. 2 is defined by glass substrates 11A and 11B opposed to each other, and a discharge gas is filled between the glass substrates 11A and 11B.
The glass substrate 11A may be referred to as a front or display-side substrate facing a viewer of the display panel 11, and the glass substrate 11B may be referred to as a rear substrate provided across the glass substrate 11A from the viewer.
More specifically, the glass substrate 11A has the first and second discharge electrodes X1 through Xm and Y1 through Ym alternately arranged with the same pitch on its side opposing the glass substrate 11B. The glass substrate 11B has the address electrodes A1 through An formed on its side opposing the glass substrate 11A. The first and second discharge electrodes X1 through Xm and Y1 through Ym are formed of a transparent conductive film of ITO (In2O3.SnO2), and the first discharge electrodes X1 through Xm (ITO electrodes) has low-resistance bus electrodes x1 through xm formed thereon, respectively. Similarly, the second discharge electrodes Y1 through Ym (ITO electrodes) has low-resistance bus electrodes y1 through ym formed thereon, respectively. On the other hand, the address electrodes A1 through An are formed of low-resistance metal patterns to extend in a direction to cross a direction in which the bus electrodes x1 through xm or y1 through ym extend. The first and second discharge electrodes X1 through Xm and Y1 through Ym and the bus electrodes x1 through xm or y1 through ym are covered with a dielectric film 11a on the glass substrate 11A, and the address electrodes A1 through An are covered with a dielectric film 11b on the glass substrate 11B. Further, as is not shown in the drawing, phosphor patterns of red, green, and blue are applied and formed on the dielectric film 11b in accordance with display pixels.
In the display panel 11 of the above-described structure, discharges caused between the glass substrates 11A and 11B excite the phosphor patterns to produce light, which is emitted through the glass substrate 11A as indicated by arrow in FIG. 2.
FIGS. 3(A) and 3(B) are plan views of patterns of the first and second discharge electrodes X1 through Xm and Y1 through Ym formed on the glass substrate 11A in another conventional ALIS-type plasma display device including the display panel 11. The X and Y directions of FIGS. 3(A) and 3(B) correspond to those of FIG. 1.
According to FIG. 3(A), the first and second discharge electrodes X1 through Xm and Y1 through Ym are formed of series of repeated T-shaped ITO patterns (electrodes) XT and YT extending from longitudinal sides of the corresponding bus electrodes x1 through xm and y1 through ym on the glass substrate 11A, respectively. Each ITO pattern has a tip part TA of a width A that extends in the extending direction of the bus electrodes x1 through xm or y1 through ym and a narrow neck part TB connecting the tip part TA and a corresponding one of the bus electrodes x1 through xm or y1 through ym. Each adjacent ITO patterns are arranged with a pitch corresponding to the resolution of the display panel 11, for instance, a pitch of 300 xcexcm in FIG. 3(A), and a discharge is sustained in a gap (discharge gap) of a width g formed between each opposed ITO patterns XT and YT.
FIG. 4 is a diagram showing a structure of the glass substrate 11B of FIG. 2.
According to FIG. 4, ribs 11C are formed with given pitches on the glass substrate 11B to extend in the Y direction of FIG. 1. Grooves G1 through Gn are formed between the ribs 11C, and the address electrodes A1 through An are formed in the corresponding grooves G1 through Gn. Further, the address electrodes A1 through An are covered with the dielectric film 11b in the corresponding grooves G1 through Gn, and the phosphor patterns R, G, and B of red, green, and blue, respectively, are formed on the dielectric film 11b. 
The glass substrate 11B of FIG. 4 is reversed to be placed on the glass substrate 11A so that, as shown in FIG. 5, the grooves G1 through Gn formed between the ribs 11C contain the corresponding ITO patterns XT and YT. In FIG. 5, the ribs 11C are indicated by broken lines for easy understanding of the drawing.
Thus, the plasma display device having the electrode structure of FIG. 3 can reduce power consumption and a driving voltage by employing the T-shaped discharge electrode patterns XT and YT. However, since the ITO film forming the discharge electrode patterns XT and YT has a thickness of 1 xcexcm or less, any discharge electrode pattern XT or YT can be broken by slight unevenness of the surface of the glass substrate 11A as indicated by a circle in FIG. 5. Such breakage prevents a desired cell from emitting light, thus resulting in a defective display.
Therefore, in order to secure a normal display even in the case of such breakage of any discharge electrode pattern XT or YT, the inventors of the present invention have proposed in Japanese Laid-Open Patent Application No. 2000-251739 auxiliary electrodes P to be provided, in the case of FIG. 5, to the bus electrodes x1, x2, y1 and y2 so as to extend to the tip parts TA of the discharge electrode patterns XT and YT. By providing the auxiliary electrodes P, even if the neck part TB of the discharge electrode pattern XT is broken as shown in FIG. 5, a desired discharge voltage can be supplied via the auxiliary electrode P from the bus electrodes x1 to the T-shaped tip part TA of the discharge electrode pattern XT.
FIG. 6 shows another auxiliary electrode Q.
According to FIG. 6, the auxiliary electrodes Q stem from the bus electrodes x1, x2, y1, and y2 to extend along the neck parts TB of the discharge electrode patterns XT and YT. If the neck part TB of the discharge electrode pattern YT is broken as indicated by a circle in FIG. 6, a driving voltage is supplied via the auxiliary electrode Q from the bus electrode y2 to the tip part TA of the discharge electrode pattern YT. However, since the auxiliary electrodes Q of FIG. 6 are formed in the light-emitting parts of display cells, the brightness of the plasma display panel 11 is reduced. In this point of view, the auxiliary electrode P of FIG. 5 is preferable to the auxiliary electrode Q of FIG. 6.
FIGS. 7(A) and 7(B) are schematic diagrams each showing a discharge caused in a cell in a plasma display panel including the T-shaped discharge electrode patterns XT and YT. FIG. 7(A) shows the discharge caused in the plasma display panel shown in FIG. 3 which panel includes no auxiliary electrodes P and Q, while FIG. 7(B) shows the discharge caused in the plasma display panel shown in FIG. 5 which panel includes the auxiliary electrodes P.
By comparing FIGS. 7(A) and 7(B), it can be seen that a discharge area is substantially larger with the auxiliary electrodes P in FIG. 7(B) than in FIG. 7(A). This is attributed to an increase in a discharge current which increase is caused by an increase in an effective electrode area which increase results from the formation of the auxiliary electrodes P.
Such an increase in the discharge current increases electrical connection between neighboring cells in the same groove with the result that charged particles, particularly, electrons, may diffuse to and accumulate in neighboring cells. If the electrons thus diffuse to and accumulate in the neighboring cells, residual ions accumulate in a selected cell so that a consequent potential difference may cause a large-scale giant electric discharge across a plurality of neighboring cells as shown in FIG. 8. Such a giant electric discharge may be caused without the formation of the auxiliary electrodes P, but the formation thereof increases the risk of such an uncontrollable giant electric discharge without doubt.
Further, if the ribs 11C includes a defective one as shown in FIG. 9, charged particles generated in a selected cell can diffuse to a neighboring cell separated by the defective rib 11C through a defect thereof and may cause an uncontrollable abnormal discharge in the neighboring cell. These discharges are visually recognized as display defects.
It is a general object of the present invention to provide a novel and useful plasma display panel in which the above-described disadvantages are eliminated.
A more specific object of the present invention is to provide a plasma display device free of display defects resulting from a defective discharge electrode and an abnormal discharge by means of auxiliary electrodes.
The above objects of the present invention are achieved by a plasma display device including: first and second substrates sandwiching a discharge gas therebetween; a plurality of first and second electrodes arranged alternately on the first substrate to extend in a first direction; a plurality of third electrodes arranged on the second substrate to extend in a second direction perpendicular to the first direction; display cells formed between the first and second electrodes along the third electrodes; first and second discharge electrode parts extending from the first and second electrodes toward the second and first electrodes in the display cells, respectively; and first and second auxiliary electrodes connecting the first and second electrodes with tip parts of the first and second discharge electrode parts, respectively, wherein the display cells include first and second display cells, the first display cells including the first and second auxiliary electrodes, the second display cells each lacking at least one of the first and second auxiliary electrodes.
According to the above-described plasma display device, a giant abnormal electric discharge apt to occur in a plasma display panel having T-shaped discharge electrodes and bus electrodes connected by auxiliary electrodes is prevented effectively by forming and dispersing display cells without the auxiliary electrodes in a plasma display panel. A discharge area in a display cell without the auxiliary electrodes P is smaller than in a display cell with the auxiliary electrodes P. Consequently, the spread of the giant abnormal discharge from cell to cell is prevented by forming such a display cell without the auxiliary electrodes P.
The above objects of the present invention are also achieved by a plasma display device including: first and second substrates sandwiching a discharge gas therebetween; a plurality of first and second electrodes arranged alternately on the first substrate to extend in a first direction; a plurality of third electrodes arranged on the second substrate to extend in a second direction perpendicular to the first direction; display cells formed between the first and second electrodes along the third electrodes; first and second discharge electrode parts extending from the first and second electrodes toward the second and first electrodes in the display cells, respectively; first and second auxiliary electrodes connecting the first and second electrodes with tip parts of the first and second discharge electrode parts, respectively; and partition walls formed on the second substrate and separating arrays of the display cells in the second direction from one another, the partition walls having their thicknesses increased in specified ones of the display cells, wherein the display cells include first and second display cells, the first display cells including the first and second auxiliary electrodes, the second display cells each lacking at least one of the first and second auxiliary electrodes, and the third electrodes are formed in spaces partitioned by the partition walls.
According to the above-described plasma display device, the same effects as described above can be produced.